Q&A: Leonard Guarente

LG: This gene came out of studies of aging in yeast. We started those studies in 1991, and the question we wanted to answer was, Do yeast cells age? And if they do, are there one or a small number of genes that are particularly important in dictating the life span of these cells? For four or five years we published nothing because we were just banging away at the problem. It took eight years before we could come to the conclusion that this one gene, SIR2, influenced the life span.

TR: The gene also promotes longevity in worms and fruit flies. What seems to be its common role?

LG: The idea would be that when food is scarce it is an advantage to be able to recognize the scarcity and slow down aging and reproduction, to postpone reproduction for when food becomes available again. And now there is some evidence that this is in fact the case.

TR: Is this also true in humans?

LG: It is a good hypothesis that something like this will be true in mammals. And there are hints. But I would say there is no conclusive evidence yet. But we know that the mammalian version of SIR2, which is a gene call SIRT1, has at least some of the activity in cells that one would anticipate for a life-extending function. What needs to be tested is whether it affects aging in the whole organism.

TR: How large is this effect of calorie restriction on aging in rodents?

LG: Studies show this diet could extend life up to 50 percent. So, it is pretty substantial. But there are people out there claiming science will allow people to live thousands of years. I tend to believe that is a lot of bunk. But the opportunity we do have is nothing to sneeze at. I think it is the major opportunity that Mother Nature has given us to intervene in the aging process. And by intervene I mean not just to promote longevity but to fight diseases.

TR: Other researchers are testing the antiaging effects of calorie restriction in monkeys, aren’t they?

LG: Those studies have been going on for some 15 years now. I know of two studies, and both are reporting that the diet induces the same physiological changes as in rodents, which is a very good indicator. There’s no report yet on whether it makes the monkey live longer, because that data takes a long time to be available. But I think we’ll know quite soon.

TR: Is all the hype a good or bad thing for antiaging research?

LG: It cuts both ways. The good part is where there is public interest, there is funding available for the research. The bad thing is that if the work does get overhyped in the media it raises false expectations. I get asked a lot, “What is taking so long?”